Hundreds of police officers are clearing protesters from Los Angeles and Philadelphia, arresting those refusing to leave and dismantling tents.

Wednesday morning's forcible evictions of Occupy camps have so far avoided the violent scenes played out in Oakland and Wall Street, where teargas, pepper-spray and non-lethal projectiles were used to disperse people. However, there were 200 arrests in Los Angeles alone, according to police.

In Los Angeles around 1,400 officers wearing riot gear and biohazard suits were moving members of Occupy Los Angeles after they ignored a Monday deadline to leave the area.

Protesters moved into the City Hall park on 1 October and, within weeks, their encampment had grown to include 500 tents and up to 800 full-time residents. But numbers fell last week after the Los Angeles mayor, Antonio Villaraigosa, issued an ultimatum, telling them to move out at the beginning of this week or face eviction.

Villaraigosa had earlier been friendly toward the protesters, but said the group had to go when the city's officials started complaining of crime, sanitation problems and property damage.

The final straw appears to have been reports of children staying at the camp. In an interview with the Los Angeles Times earlier this week, the mayor said: "The chaos out there could produce something awful".

Occupy LA remained defiant, unfazed even, as eviction day loomed.

A blog on its website, posted on Sunday evening, said: "The Occupation Movement, if nothing else, is agile and adaptable. "We travel light. So whether or not the eviction features the drama the news organisations are hoping for, the occupation of Los Angeles will survive.

"Thankfully, the elements and hardships suffered elsewhere have not been a factor here. The people that have occupied City Hall for the last 58 days will move, regroup, perhaps relocate, perhaps reoccupy. There are many voices here, many opinions, many motives."

Before the police arrived protesters were upbeat. One wore a Santa Claus hat and danced in the street, another showed off the reindeer antlers she had attached to her gas mask.

Fireworks exploded in the sky at one point. Later, as helicopters hovered above, someone blew "The Star Spangled Banner" on a horn.

As officers first surrounded the camp, hundreds of protesters chanted: "The people united will never be defeated."

In the first moments of the raid, officers tore down a tent and wrestled to the ground a tattooed man with a camera on City Hall steps.

Teams of four or five officers moved through the crowd making arrests one at a time, cuffing the hands of protesters with white plastic zip-ties. A circle of protesters sat with arms locked, many looking calm and smiling.

Some activists accused Villaraigosa of violating the constitution and of using the presence of vulnerable people at the camp as a smokescreen for eviction.

In a statement explaining Wednesday's eviction, the mayor said: "We have taken a measured approach to enforcing the park closure because we have wanted to give people every opportunity to leave peacefully. I ask that anyone who remains in the park to please leave voluntarily.

"Our approach also recognised the human need in the encampment. Since the park closure was announced on Friday, outreach workers with the Los Angeles Homeless Services Authority have walked through the park, assessing needs and connecting interested individuals in need with an alternative place to spend the night.

"During the park closure, a First Amendment area will remain open on the Spring Street city hall steps. Once the park is cleared, it will be repaired and returned to all Angelenos to exercise their First Amendment rights."

In Philadelphia, police began pulling down tents at about 1:20am (EST) after giving demonstrators three warnings that they would have to leave, which nearly all of the protesters followed. Dozens of demonstrators then marched through the street until they were stopped by police.

Philadelphia police commissioner Charles Ramsey said breaking up the camp in the early hours helped minimise disruption to businesses and traffic.

Six protesters were arrested after remaining on a street that police tried to clear. The eviction overall appeared to have been carried out without any significant scuffles or violence.

"This is a symbolic action, but in another sense this has been our home for almost two months and no one wants to see their home taken away from them," said 22-year-old Philadelphia protester Bri Barton, while acknowledging the movement would have to leave the site.